The present invention relates to a fire-resistant laminate structure and more particularly to horizontally hinged doors for floors that have a high fire rating and which use an automatic control system to automatically close the door in a fire.
The need for fire resistant structures is self-evident and building codes have been passed by governments to ensure that public safety is protected. Such building codes mandate fire-resistant materials such as panels and mechanisms to prevent the spread of fire. Structures such as floors, ceilings, and doors must have resistance to the path of the fire and many techniques have been used to produce such fire resistance.
Horizontally-hinged doors may be used for access doors, roof scuttles, automatic fire vents, ceiling access doors, etc., to provide access from one location to another location such as through a floor into a space between the floor and ceiling below. Such openings are a safety hazard in the event of fire because they present a path to the spread of the fire. Therefore, most fire codes mandate that such openings be closed with fire-resistant materials. It is also necessary for these doors to be automatically closed in case of fire.
The industry standard uses ASTM E119 to define a maximum temperature rating on the unexposed surface to prevent the effect of a fire on the floor below from causing fire damage to the floor above.
Generally, some sort of insulation is required on fire-resistant doors. To achieve ASTM-E119, earlier doors have used either a thick (usually four inch) layer of insulation comprised of mineral wool or fiber board and air within the door structure, or have coated the door with an intumescent material. As used in the present document, “intumescent material” shall be defined as “a material that, upon exposure to heat or flame, swells or puffs up to a relatively thick cellular foam char which possesses heat-insulative and fire-retardant properties.”
A problem with mineral wool-insulated doors is that the insulative property of the mineral wool is such that a thick layer, usually four inches, must be used to pass the ASTM E119 standard. This requires the door to be at least this thick.
A problem with earlier intumescent materials is that by themselves they do not provide sufficient insulative properties to meet ASTM E-119. An example of a fire door constructed with such material is disclosed in U.S. Pat. No. 5,554,433 (Perrone et al.), herein incorporated by reference. Perrone requires a layer of cementitious material on the door surface opposite the surface on which the intumescent material is applied. According to Perrone, this cementitious material acts as a thermal barrier and insulator and also serves to dissipate the heat that penetrates the structural material of the door by steam produced from water in the cement. The cementitious material is layered onto the door after it is sold, and greatly increases the weight of the door.
U.S. Pat. No. 4,799,349 (Luckanuck), herein incorporated by reference, discloses a steel fire door with a central core filled with mineral wool. The mineral wool is bonded to the inner surfaces of the steel sheets forming the door by a binder comprising a mixture of alkali metal silicate and a mineral powder that causes the binder to intumesce under high temperature, thus protecting the mineral wool against the heat.
A problem with Luckanuck is that the mineral wool is a fiber sheet that completely fills the hollow core of the door, leaving no space within the hollow core for door hardware. Also, Luckanuck is not disclosed as having an aluminum door. Aluminum softens at about 400° C. and melts at about 600° C. (see U.S. Pat. No. 4,888,507, herein incorporated by reference).
There is a need for a fire-resistant floor door that overcomes the problems discussed above. In particular, there is a need for a fire-resistant floor door that may be constructed of aluminum, with an intumescent coating on the outside surface of the door facing the fire, and with a hollow central core without insulating material that may be used to hold door hardware such as the handle, and without the need for a cementitious layer on the outside surface of the door away from the fire.
There is also a need for an improved self-closing mechanism for a fire-resistant door that is substantially less complex and less expensive to manufacture than that disclosed in Perrone.